Totally agree with all the above! My son is three, and has been potty trained for 2 months now. He's had (ONLY!) a handful of nighttime accidents, but that's ok
We started talking about how cool it was to use the potty when he was around 2-ish, and then a couple days after his third birthday, I casually mentioned that when he was ready we could go buy some big boy underwear whenever he was ready. We went that day, and he never wore diapers again! I bought one of those toddler seats that go over the toilet, and in a few minutes he had the hang of it! I'd say the first three days he had a little bit of trouble getting there in time, but we didn't make a big deal out of it, and soon it wasn't a problem at all.
My advice, start talking about it now, but not in terms of her having to do it, just that you use the potty, other big girls and boys use the potty and how fun it is! (lol- oh the life of a toddler mom!) Don't push. And, some may disagree, but skip the training pants all together (except at night, if you feel you need them, we never used them at night and just cleaned up accidents).
Good luck! Don't put pressure on yourself! It's ok, really!